Multiple-switchboard system



(No Model.)

T. SPENCER 85 .T. G. WALES, Jr.

MULTIPLE SWITUHBOARD SYSTEM.

' S Patented Dec, 10, 1895.

.No. 551,055. E13

ANDREW 'EGRAHAM. PHOTO-UTND-WASHIN GTDNJLQ UNITED STATES PATENT OFFICE.v

THEODORE SPENCER, OF. CAMBRIDGE, AND THOMAS C. ALES, JR., OF BOSTON,ASSIGNORS TO THE AMERICAN BELL TELEPHONE COMPANY,

OF BOSTON, MASSACHUSETTS.

MULTIPLE-SWITCHBOARD SYSTEM.

SPECIFICATION formingpart of Letters Patent No. 551,056, dated December10, 1895.

Application filed March 18, 1896.

To all whom it may concern:

Be it known that we, THEODORE SPENCER, residing at Cambridge, in thecounty of Mid-. dlesex, and THOMAS C. WALES, J r., residing at Boston,in the county of Suffolk, State of Massachusetts, have invented certainImprovements in Multiple Switchboard Systems, of Whichthe following is aspecification.

This invention relates to multiple switchboards for telephone-exchangesor central stations and to the species illustrated and described inLetters Patent of the United States No. 252,576, granted to Leroy B.Firman, January 17, 1882, in which the main circuits from thesub-stations pass to the several switchboard-sections and arerepresented on the said sections by independent normally-discontinuousbranch terminals in the form of plug-sockets. We associate with thisform of switchboard means whereby the subscribers at the sub-stationscan call the operator at the central station and whereby the saidsubscribers transmittingtelephones are rendered operative, such meansconsisting of a source or generator of electricity located at thecentral station incircuit with and common to all of the sub-stationcircuits connected thereto. A telephone interconnecting systemillustratin g such means is shown in United States Patent No. 528,040,granted to Theodore Spencer October 23, 1894. In this patent, however,separate generators of electricity are used for calling andconversational purposes.

In the modern telephone-exchange all of the circuits are carried throughthe central office with double wires or conductors, and the substationcircuits connected therewith maybe either of double or metallicconductors or of grounded conductors.

extendthrough the several sections of the switchboard with normally-openbranch terminals in a socket at each section, each con-' ductor beingconnected through a separate coil of the line-annunciator in such mannerthat the annunciator is operated by means of terminating at the oppositepoles of a gener- \Ve provide for I both kinds of circuits. Theconductors thereof Serial No. 542,218. (No model.)

ator of electricity common to all of the substation conductors.

When any sub-station wishes to call the central station, the telephoneis removed from its hook, which act closes the circuit of the commongenerator of electricity, and the operating-coil of the line-annunciatorbeing energized, its target is displayed. The insertion of one of a pairof looping-plugs into the answering-jack of the circuit closes a localbattery-circuit through a third coil of the line-annunciatorand resetsthe said annunciator, and by means of a suitable bridgingkey theoperators telephone apparatus is brought into circuit with thesub-station. WVe associate between the cords of each pair oflooping-plugs an amplification of the means shown in United StatesPatent No. 474,323, granted to H. V. Hayes May 3, 1892, for energizingthe transmitting-telephones at the sub-stations and for repeating fromone substation circuit into another.

The local battery-circuit by means of which the annunciator is resetforms a portion of the test-circuit and has branches to each jacksocketof the same sub-station circuit at each section of the switchboard, andalso has a connection with one pole of the said common generator ofelectricity, and when the tip of the test-plugof a pair of looping-plugsis in contact with the test-ring of the socket of a called circuit, ifthe circuit is busy the usual click is heard inductively in theoperators telephone.

The invention also relates to a form of lineannunciator having threecoils, located end to end, two of the coils being connected in with thecircuit-conductors, one in each conductor, forming a balance, but onlyone of them is in a position to operate the annunciator, the third coilserving to automatically reset the annunciator.

The open terminal multiple switchboard, provided with a common generatorof electricity for sub-station calling and conversational purposes,represents the latest improvement in interconnecting systems, and inintroducing it at places where the ordinary system is in use, in whicheach substation is provided with independent call-sending appliill .uating the line-annunciators, and with independent local batteries forenergizing the telephone-trailsmitters, may still use these appliances,and obtain service through the cen traloflice circuits described herein,all of which we will now proceed to describe and specifically point out.

In the drawings which form. part of this specification, Figure 1 is adiagram illustrative of the invention, showing schematically a centraloffice A, to which are connected the sub-stations O and D, arranged tobe operated by means of a centralized generator of electricity, and a.third sub station B, provided with a. local means for calling andspeaking. Fig. 2, is a diagram to illustrate the method of testing, andFig. alongitudinalsection of the line-annunciator employed in connectionwith the invention.

A designates so much of the central office as is necessary to show theworkings of the invention, and consists in the apparatus shown,comprising a pair of looping cordsand plugs P P having their sleevesconnected by wires 11 and 12 throughtwo windingsi and'if, of arepeating-coil I, and their tipsconnected together by the wires 10, 15,14:, and 13 through two windings i and 2' of the repeating-coil I- Anelectric generator G is 0011- nected in between. the points, 16 and 17,to which the windingsvl and i are also respectively connected. \Ve maywind the four helices 13 11 i 1' upon one core, one over the other, orwe may employ two separate repeating-coils consisting of two. helices orwindonly.

The ringing and listening keys being well known and standard appliancesare not shown.

Contacts 21 and 22, connected at theends of wire 18, bridging the wiresand 11, (but shown as not touching said wires, indicate that theoperators telephones t and we may be connected in, the wire 18,including winding 71 of induction-coil 1 receiving telephone t andcondenser 20..

The battery 7; and transmitter 'm, are bridged in between the primarywindings '6 and t" of the coil 1 and 2' is a secondary winding includedin wires 23 and 2%, which include the telephone t in a local circuit.

Conductors 25 and 26 extend from. points 16 and 17', respectively, andform continuations from the poles of the generator G to the doubleconductors 30 and 31 of the sub-station circuits 0 and D, the. formerrepresenting a grounded line and the latter a complete metallic circuit.At each sub-station, when the telephone is on its hook, a circuit is001m pleted through a high-resistance bell r, and when the telephone isdetached from its hook a, circuit is completed through the telephonesEach conductor 30- comes to each "section of the switchboard by branches0,

which terminate intip-springs 2,and each con ductor 31 comes to eachsection by branches (Z, which termin ate in rings 1 both the sprin gsand rings beingin a socket. The conductor 30 extends through the coil 9of the line-annunciator E and connects with the conductor 25, and theconductor-3l extends through the coil f upon the same core and connectswith conductor 26.

The locking-coil g of the line-annunciator is connected on one side bywire 6 with the springs} and by wire 5. with the. test-rings z of eachsocket and from its other side by wires 50, 39,, and 7 to. the springs 1of each socket, including the testing batteryp. -From a point 28 on thewire a. wire 27 extends to the upper pole of the common generator Gr.Between the tips of both plugs P and P inay be placed theautomaticclearin grout annun- ;head 33 integral therewith.

ciators or signals 71- and 7L2, similar tothose dcscribed in Patent No.530,104, granted March {19, 1895, uponthe application of TheodoreSpencer.

Fig. 3-. is a longitudinal section of the lineannunciator, consisting oftwo soft-iron cores i0! and 43, provided with brass or other nonmagneticmetal ends. or partitions 4-1 and 42, joined end to end. in any suitablemanner,

inclosed in a. soft-iron sheath 45, having a The core 40 is wound with,two. coils f and a, separated by a soft-iron washer or partition 44*,the end of ,the coil 6 being closed by a hard-rubber washer 417. is. anarmature pivoted at 4.8 and pro vided with an arm 34;, which extends. tothe natesiln a hook, asv usual. A pivoted shutter 35 and a pivoted catch4.9 for the same are provided in awell-known manner. As there is acompletemetallic envelope constituting a magnetic circuit aroundthecoilf by reason of the core 450, the washer 44,, and the outer sheath45, the coil has Ito-magnetic effect upon the armature, its ofiice beingtopreserve the balance of the circuit, the coil 6 operating the armature457.

The operation of the invention is asfollows:

Then the subscriberat a substation wishes to conversewith anothersub-station, the telephone If is removed from its hook, which rises andmakesa circuit. through its back contact with the wire 5, shunting thehigh resistance of the bell 1'. Current from the common generator Gcirculates in the circuit and through coil 6 of the line-annunciator,causing the shutter 35 to be displayed. The operator introduces. theanswering-plug into the answering jack or socket of the circuit, the tipof the plug'making contact with the open terminal spring 2 of conductor30 and the sleeve making contact with the ring y, connected to the othercircuit-conductor 31, and also with the ring .2, connected with thetest-circuit, and the metal ring of the plug unites the open springs 1and 3 of the local circuit, including the battery 19 and the coil 9 ofthe line-annunciator, energizing its core and attracting and holding theshutter 35 thereto, thus resetting the same. We now have a circuit fromone pole of generator G through winding tot coil I, wires 15 and 10 totip of plug P, spring 2 of the subscribers jack, wires 0 and 30 to thesub-station, returning by wire 31 and branch (1 to ring y, thence bysleeve of plug P, wire 11, and winding i of the repeating-coil. I to theother pole of the generator G. As the current from the generator G isnow flowing in the circuit thus established, the sub-station transmitterm can be used for conversation. The operator having connected inthetelephones on and t the circuit wanted by the subscriber isascertained. The tip of the plug P is now placed in contact with thetest-ring .2 of the called circuit, and if busy a click is heard in theoperators telephone 25, and if not busy no sound is heard. Referring toFig. 2, which shows the operators outfit and the test-circuit, with theanswering-plug inserted in a socket and the test-plug in contact withthe test-ring of the called circuit, it will be seen that when theoperators receiving-telephone is connected in between thecord-conductors and when the tip of the testplug is in contact with thetest-ring of the called circuit a local circuit is established from onepole of the battery p by wire 27, winding 71 of induction-coil I, wire13, tip of plug P test-ring z, wire 5 to spring 3, across the unitingmetal contact of one of the looping-plugs in the called line to thespring 1, and by wire 39 to the opposite pole of the batteryp,and thesudden rush of current through this local circuit from battery 19induces in the winding i a current of the opposite sign or polarity andoccasions a disturbance in the condenser 20, in the local circuitincluding the generator G, windings t' 2' of the induction-coil I, wires10 and 11, and the wire between the contacts 21 and 22, which producesthe click in the operators telephone. If the desired line is found bythe application of this test to be not in use, the operator inserts plugP into its socket and by means of the usual ringing-key andcontinuouslyoperating call-generator (not shown in the drawings) sendsto line a current sufficient to operate the high-resistance bell r, aswill be understood, and when the called subscriber removes his telephonefrom the hook, shunting his callbell, a talking-circuit is establishedbetween the two connected subscribers. We have already traced one sideof this circuit through generator G and the windings 2' i ofrepeating-coil I. The circuit of the called subscriber now has a sectionin com- CAI mon with that of the calling subscribertowit, that portionof the circuit which is between the points 16 and 17 and which includesvthe generator Gr. The circuit of the-called subscriber, beginning atpoint 16, is-as follows: winding 71 of coil I, wires 14: 13 to tip ofplug P thence by spring 2 of the springjack of the called subscriber,branch 0, and wire 30 to his station, returning by wire 31 and branch clto ring y of the plug-socket. The circuit continues from this point bywire 12 and winding 1 of the repeating-coil to point 17 on the otherside of generator G,which completes the circuit. In this compoundcircuit the windings i 2' of the repeating-coil are in the circuit ofone subscriber and the windings 2' 11 in the circuit of the othersubscriber, the two circuits being thus connected inductively forconversation purposes, while the battery is in a section common to thetwo circuits.

When at either of the connected sub-stations the telephone is returnedto its hook, the

circuit is closed through the high-resistance bell 1, which issubstantially like opening the circuit, owing to the high resistance ofthe coils of the bell, (about five thousand ohms,) and the clearing-outsignal it or 71, is operated to notify the operator to disconnect. Thesaid clearing-out signal will preferably be of the kind illustrated inFig. 6 of Patent No. 536,104 ah'eady referred to. So long as thetalking-circuit is closed the signal-plate is withdrawn from view; butwhen the circuit is opened by hanging the telephone on its hook thesignal-plate is automatically displayed, giving the signal todisconnect.

- B indicates a sub-station provided with a magnetogenerator 7 O in anormallyopen bridge 71, a high-resistance call-bell 72 in a closedbridge 7 3, and telephones in normallyopen terminals of the conductors ab. At the central station conductor a is closed to conductor I) throughthe coils e and f of the lineannunciator E, which are joined to eachother at 9, and conductor a ends in open terminal springs 2 andconductor 6 in rings y in each socket j. The wires 7 and 8 extend fromthe opposite poles of the battery 19 and include the locking-coil g ofthe line-annunciator and terminate in the springs 3 and in springs 1 andtest-ring 2, respectively, the locking and testing circuit being thesame in arrangement and operation as in sub-station circuits 0 and D.The line-annunciator E is the same as used at the sub-stations O and D,except that the coils f and e are united, and operating the generatorcauses its shutter to fall in the usual manner. In this combination ofcommon battery and magneto-generator circuits there is provided aseparate clearingout annunciator for the latter class between each pairof cords and plugs, which can be operated by the magneto -generator 70,as shown in Fig. 1.

n is the annunciator in a r closed local circuit 19 and is in inductiverelation to the induction-coil I by means of the windings t, and itsoperation will be readily understood.

By the above means-both classes of circuits can be interconnected anddisconnected with facility, the same test system being used for both,and when a magneto generator circuit is changed to a commonbattery-circuit the same line-annunciatorscan beused, the coils f and gbeing placed in separate circuits, as described, and the temporaryclearing out annunciators n be removed altogether. \Vhere it isspecified in the description and claims that the circuit of generator-Gis non mally open at the subscribers stations, it is meant that thecircuit is practically and properly regarded as open until thetel'ephoneI is removed from its support, the resistance of bell '1 being such thatno appreciable current from the generator can pass through the branch w.

Having fully described our invention, we claim- 1., Two telephonecircuits, each extending from a substation to: the same central stationand completed or closed through a see tion of conductor common toboth,which common conductorincludes an electrical genorator, and a repeating"coil having two sections respectively interposed between the oppositepoles of said generator and the-two 5 conductors of the said circuits,each section having one of its windings included in each of the said twocircuits, respectively.

2. Two telephone circuits, each extending from a substation to the same:central station and completed or closed through a section of conductorcommon to both, which common conductorincludes an electrical generator,and four repeating induction coil windings interposed respectivelybetween the twopoles of said generator and the conductors of the saidcircuits having two of the said four windings included in each of thesaid two circuits, in inductive relation to" the other two saidwindings.

3-. The combination of a multiple switchboard at a central station, andtwo or more substations the circuit conductors of which are providedwith normally open terminals at each section of the switchboard and areclosed through a common generator of electricity at the central stationwith looping cords and plugs bridged by a conductor which includes thesaid common generator and a repeating coil whose'windings are interposedbetween the poles of the generator and the two conductors of the saidcords, and included therein.

4. The combination of a multiple switchboard at a central station, andtwo or more substations, the circuit conductors of which are providedwith normally open terminals at each section of the switchboard andareclosed through a common generator of electricity at the centralstation; with looping cords and plu gs bridged bya conductor whichincludes the said common generator, and a 1 repeating coil, divided intofour windings, interposed between the two poles of the said generatorand the conductors of the said cords, the windingsbeing included in the1 said cord conductors.

5. The-combination ofa central station and j a substationthe conductorsof which are nor mally open at the substation and closed through ageneratorof electricity at the central station; a line annunciatorhaving two coils, one being included ineach conductor of the circuit,one coil being magnetically inop- I erative, and means atthe substationincludingthete'lephone' circuit switch for automatically closing thecircuit to send thecall signal.

6. The combination of amultiple switchjboard at a central station, andtwo ormore substations, the circuit conductors of which 1 are normallyopen at the substations and provided with normally open terminals ateach section of the switch-board, and closed 1 through a commongeneratorof electricity at the cent al station; with line annunciators Ihaving three coils one" being included in each conductooi the circuit(one of which coils is Q magnetically inoperative) thethird coil beingQincluded in a normally open locking circuit having twoopen terminals ateach section of gtheswitchboard and a battery. 7 7.. The combination ofa multiple switch- 1 board at acen-tral station and a substation thecircuit conductorsofwhich are normally open at thesubstation andprovided with normally open terminals at each section of the switchboard and closed through a generator ol' electricity at the centralstation; with a line anj-nu-nciator having three coils one beingincluded in each conductor of the circuit, (one of which coils ismagnetically inoperative,) the third coil being included in a normallyopen locking circuit having" two open terminals at each section ofthe-switchboard and a battery, means at thecentral station, congsistingof a plug, for closing the open termii nals inthe locking circuit at anysection of jthe switchboard. j 8. An annunciator consisting of twobobbins havingsoft iron cores separated-by a non magnetic partition onebobbin being divided by a magnetic partition, and wound with two coils,the other bobbin having one coil; both bobbins inclosed in a soft ironsheath closed at one end, its opposite end being closed by an insulatingring; and a pivoted armature having a hook or catch upon its extremityto engage a pivoted signal shutter.

9. The combination of a switcl'iboard at. a central station and two ormore substations whose circuit conductors extend to each section of theswitchbo rd and are-provided there with open switching terminals, thesaid circuits including a common generator of electricity at the centralstation; a plurality of pairs of looping cords and plugs having a bridgeconductor between the conductors of L each pair of cords includingthesaidcommon generator of electricity and a repeating coil IIO as setforth; and an operators telephone in inductive relation with saidrepeating coil and with a normally open local test circuit including abattery, adapted to be closed by the insertion of a plug of one pair ofcords and the test plug of another pair of cords.

10. The combination of a multiple switchboard at a central station, andtwo or more substations, the circuit conductors of which are providedwith normally open terminals at each section of the switchboard and areclosed through a common generator of electricity at the central stationa local test circuit for each substation circuit including two openterminals at each switch board section and a battery with a branchconnection to one pole of said common generator; means for closing saidtwo open terminals at any switch-board section to complete the testcircuit and for placing the operators telephone in inductive relationthereto said means consisting of looping cords and plugs bridged by aconductor which includes the said common generator and a repeating coilwhose windings are interposed between the poles of the generator and thetwo conductors of the said cords and are included therein; and aconductor bridged between the two conductors of the said cords includinga condenser and the operators telephone.

11. The combination substantially as hereinbefore described of a seriesof main telephone circuits converging from a number of substations to acentral station; a branch terminal multiple switch-board at said centralstations with which the said main telephone circuits are associated; acommon generator connected directly in such circuits normally as asource of signaling currents; and in bridge or derived circuit with anytwo united circuits as a source of voice currents, and a repeatinginduction coil associated with said battery and adapted to be placed incircuit with said two united substation lines, substantially asdescribed.

12. The combination in a telephone exchange system with a branchterminal multiple switchboard; of a source of current common to a numberof circuits, and supplying current for both signaling and forconversation when two subscribers circuits are connected, and arepeating induction coil adapted to be placed in circuit with twoconnected substation lines, substantially as described.

13. In combination with a switchboard at a central station and aplurality of circuits extending therefrom to substations; of a localtest circuit for each substation circuit'including two open terminals ateach switchboard section and a battery, with a branch connection to onepole of a common generator, means for closing said open terminals at anyswitch board section to complete the test circuit and for placing theoperators telephone in inductive relation thereto, said means consistingof looping cords and plugs the conductors of which are bridged by aconductor which includes the said common generator and a repeating coilwhose windings are interposed between the poles of the said generatorand the two conductors of the said cords and are included therein; and aconductor bridged in between the said two conductors of the said co'rdsincluding a condenser and the operators telephone.

14. The combination of a multipleswitchboard at a central station and aplurality of substations whose circuit conductors extend to each sectionof the switchboard and are provided there with op en switchingterminals, a part of the substation circuits being closed through acommon generator of electricity at the central station, and theremainder closed through their line annunciators; of aplurality of pairsof looping cords and plugs having a bridge conductor between theconductors of each pair of cords including the said common generator ofelectricity and a repeating coil as set forth; and an operatorstelephone adapted to be placed in inductive relation with the saidrepeating coils and with a normally open test circuit including abattery, adapted to be closed by the insertion of a plug of one pair ofcords and the test plug of another pair of cords.

In testimony whereof I have signed my name to this specification, in thepresence of two subscribing witnesses, this 14th day of March, 1895.

THEODORE SPENCER. Witnesses:

HORACE D. REEVE, JOHN C. STEVENS.

In testimony whereof I have signed my name to this specification, in thepresence of two subscribing witnesses, this 8th day of March, 1895.

THOMAS C. WALES, J R. Witnesses:

THOMAS H. LOOKWOOD, GEO. WILLIs PIERCE.

